Hourglass Narrowing, Indentation and the Hinge Effect: Shape Changes in Peyronie's Disease Beyond Curvature
Peyronie's disease can show itself not only as curvature but also as narrowing of the erect penis, an hourglass appearance, a one-sided indentation or folding at the same point (the hinge effect). This article explains why these shape changes develop, how common they are, how they are assessed at examination, why the evidence for medication and devices is limited, and why surgery is discussed differently.
Some men do not see an obvious bend in the penis; what they notice is something else. During an erection the shaft looks thinner at one point, pinched in as if by a tight belt, or there is a small hollow on one side. Sometimes the penis is firm enough, yet it gives way at the same spot during intercourse. The belief that “no curve means no Peyronie's” can delay a consultation.
Hourglass narrowing, indentation and the hinge effect are shape changes that can accompany curvature in Peyronie's disease or occur on their own; what they share is a reduced girth in one segment of the erect penis. This article looks at what these changes are, why they develop, how common they are, how they are assessed, and why treatment is discussed differently from that for curvature.
What do hourglass narrowing, indentation and the hinge effect mean?
These changes appear during an erection; in the flaccid penis they usually cannot be seen.
- Indentation (one-sided narrowing): A hollow forms over a limited area on one side of the shaft.
- Hourglass appearance: The narrowing runs all the way round the shaft; the penis is pinched in at that point and stays thicker above and below it.
- Hinge effect (instability): This is a behaviour, not an appearance. Under lengthwise load, the erect penis folds or buckles at the narrowed point.
Why do these shape changes develop?
The American Urological Association (AUA) defines Peyronie's disease by fibrosis, meaning scar-like hardening, of the sheath that surrounds the erectile tissue (the tunica albuginea). A healthy sheath expands in length and in girth during an erection, whereas the area containing a plaque cannot stretch enough. The result depends on where the plaque lies and how far it extends: a plaque confined to one side can produce an indentation, and one that encircles the shaft an hourglass appearance.
The hinge effect is the mechanical consequence of this narrowing. The more marked the narrowing and the lower the rigidity, the more easily the penis folds. The causes of shortening are covered in a separate article on our site.
How common are they?
The figures vary widely depending on who looks and how:
- European Association of Urology (EAU) guideline: States that approximately 10% of patients have atypical features, including hourglass deformity and one-sided indentations.
- A series of 703 patients from Istanbul: Notching-type deformity alone was found in 12.6% (89 patients); of these, 62.9% had a one-sided indentation and 34.8% an hourglass appearance.
- A series of 128 patients from the USA: When an erection was induced with medication and these changes were specifically sought, 65% had a volume-loss deformity: 39% a one-sided indentation and 23% an hourglass.
- A series of 1,263 patients from the USA: At ultrasound assessment, indentation or narrowing was recorded in 76.0%, an hourglass in 10.1% and a hinge effect in 33.0%.
The gap is wide because definitions are not shared and the series come from specialised centres. The common conclusion is that these changes are not rare and can be missed unless someone looks for them.
Can Peyronie's disease be present without curvature?
Yes. In a series of 1,001 patients, 12.3% had an indentation, hourglass or similar shape change with no curvature. In the series of 703 patients above, the most common presenting complaint in the notching group was not curvature but erectile dysfunction (68.5%); in 30.3% the diagnosis was made during an assessment for erectile dysfunction.
In a man with no curve, narrowing during erection, a palpable hard area or folding should still bring Peyronie's disease to mind. The phases and natural course of the disease are covered in a separate article on our site.
Why does the hinge effect make intercourse difficult?
During intercourse the penis is loaded along its length. If the shaft is of similar thickness and firmness throughout, it carries that load; if it is narrowed at one point, it can fold there. Men often describe this as “it gets hard but it bends”.
The hinge effect is independent of the measured angle: it can be present with a mild curve and absent with a marked one. In the series of 128 patients, instability was more frequent with volume-loss deformities even after the angle of curvature was taken into account (odds ratio 3.5). In a retrospective series of 1,223 patients examined by one surgeon, a girth difference of more than 1 cm was associated with a hinge effect once rigidity was taken into account.
How is it assessed at examination?
Examining the flaccid penis can reveal the plaque, but not the shape change. The EAU regards objective assessment of the deformity during erection as mandatory, and the AUA calls for an in-office assessment with a medication-induced erection before any invasive treatment. Alongside the angle, this assessment covers:
- Girth measurement: Girth is measured at the base of the penis and at the narrowed point; the difference is recorded in centimetres.
- Stability test: Gentle lengthwise load is applied to the erect penis to see whether it folds.
Before surgery, the EAU recommends documenting complex shape changes together with plaque location, penile length, erectile status and the degree of curvature. The details of angle measurement are covered in a separate article on our site.
How well do medication, injections and devices work for this deformity?
Most medication and injection studies have measured the degree of curvature; the evidence for indentation, hourglass and hinge is more limited. One systematic review notes that the intralesional injection approved in the USA is considered off-label in atypical presentations.
- Injections into the plaque: In a registry study of 86 patients, girth improved in only 3 of the 40 patients (8%) with a prominent indentation or hourglass. Of these, 35% reported that the injections had prevented the need for surgery, compared with 64% of those without indentation. The study had no control group.
- Traction (stretching) devices: The EAU cites a meta-analysis reporting about 15 degrees of improvement in curvature with traction, and adds that the effect in hourglass and hinge deformities has not been systematically studied and that, in theory, a weaker response is expected. The device needs to be used for 2–8 hours a day.
- Vacuum devices: According to the EAU, only two retrospective studies have examined the effect of vacuum therapy on its own.
The EAU offers traction and vacuum devices with a weak strength of recommendation, noting that outcome data are limited. Medication and injection options and the use of devices are covered in separate articles on our site.
Why are the surgical options discussed differently?
Plication, widely used in curvature surgery, straightens the penis by shortening its longer side; it does not widen the narrowed segment. The EAU therefore recommends shortening procedures as the first option in patients without complex shape changes such as hourglass or hinge. The routes discussed for complex deformity are:
- Plaque incision and grafting: The sheath is opened at the narrowed segment and the gap is closed with a graft. The EAU prefers this route in complex deformity without erectile dysfunction.
- Graft placed over the sheath: The indentation is filled with a graft without opening the sheath. The EAU cites a risk of erectile dysfunction of 0–2.9% and satisfaction of 85.7–100% in studies. The technique is new; the series are small and follow-up is short.
- Penile prosthesis: According to the EAU, this is considered when erectile dysfunction that does not respond to medication is also present; the AUA also lists a prosthesis as an option for erectile dysfunction and deformity that prevents intercourse. One review recommends that a prosthesis also be preferred for hinge-type instability.
In a series of 251 patients who had plaque excision and grafting, 51% of the 54 patients advised to have a prosthesis because of inadequate rigidity but who chose grafting could have intercourse after surgery, compared with 76% of the others. The timing of surgery and planning it together with a prosthesis are covered in separate articles on our site.
When should you see a doctor?
Assessment by a urology and andrology specialist is advisable if:
- You notice narrowing, a pinched-in segment or a one-sided hollow at one point of the erect penis
- The penis is firm enough but bends or folds at the same point during intercourse
- There is a palpable hard area in the penis, or erections are painful
- The shape has been changing over recent weeks or months
- Erections have weakened or the penis has shortened
- The appearance worries you or leads you to avoid intimacy
- A cracking sound during intercourse with sudden pain, sudden loss of the erection and rapid bruising (an emergency; call 112 or go to an emergency department)
Peyronie's disease is not only a matter of curvature; narrowing, an hourglass appearance and the hinge effect can make intercourse difficult regardless of the measured angle. These changes are seen on assessment during erection, and treatment is discussed differently from that for curvature. Assoc. Prof. Dr. Zülfü Sertkaya practises urology and andrology in Istanbul; assessment of shape changes related to Peyronie's disease is individualised and carried out in confidence.